The conventional prior-art linings, utilized for the protection of the shell of cylindrical grinding mills against the wearing action of the materials placed therein, change the shape of an originally circular cross-sectional grinding mill into the shape of a square with rounded corners.
The method generally utilized by the prior-art was to place cylindrical segments or truncated cylindrical segments between the shell of the grinding mill and the wear liners of the mill. These segments were hollow and normally were fabricated out of soft steel plate. As the hard alloy wear liners which were placed on the cylindrical segments began to wear out, these segments became exposed to the charge contained in the grinding mill, which would then wear through the exposed portion of the soft steel cylindrical segment. Upon being admitted into the hollow cylindrical segment, the charge had a tendency to wear into and through the curved portion, resulting in eventual grinding mill shell damage.
Various methods were utilized in an attempt to overcome these difficulties. U.S. Pat. No. 2,058,257 to Porteous describes means for securing rubber linings to the interior of the metal shell of a cylindrical grinding or crushing mill. The rubber linings are detachably retained against the surface of the metal shell by utilizing rubber-covered metal bars of substantially the same thickness as the rubber covered lining, thereby presenting a rubber surface of uniform thickness to the charge of material within the metal shell and ensuring that the life of the retaining bars is substantially the same as the life of the lining.
U.S. Pat. No. 3,431,684 to Ban discloses a rotary abrading device consisting of a drum, sealed at both ends, which is rotatable about its axis. The drum is provided with a plurality of grate surfaces forming a polygon within the drum which are loosely mounted along the inner surface of the drum so as to oscillate or jangle as the drum revolves. The grates are spaced from the inner surface of the drum and means exist for the introduction of particulate matter at the upper end of the drum while abraded particles and fines are discharged from separate discharge elements at the lower end of the drum.
U.S. Pat. No. 3,880,365 to Eigner discloses a mill having a shell which has an interior polygonal, preferably square, cross-section with rounded corners. The interior of the mill is lined by plates arranged in a series of annular courses, arranged one behind the other, at least a portion of which are inclined toward the axis and a portion of which are parallel to the axis, with adjacent courses being angularly displaced.
The helical passage formed within the mill by the offset annular courses has a sorting action on the grinding elements so that most of the larger grinding elements collect at the mill inlet end while most of the smaller grinding elements collect near the mill outlet end.
The grinding action is strongly influenced by the selection of a proper radius for the rounded corner of the shell lining. A decrease of the radius of the rounded portion relative to the diagonal measure of the cross-section of the mill results in more effective impacts upon the contents of the mill by the grinding bodies while an increase in the radius of the rounded portions has the opposite effect.
U.S. Pat. No. 4,032,075 to Tyer relates to a multi-chambered apparatus having a polygonal cross-section for scrubbing gravels and substances containing heavy precious metals. The apparatus is supported at an angle by a frame and it is adaptable to be driven by a variable speed drive system. Each section is separated from adjacent sections by a retainer ring having a circular interior opening which is preferably smaller in area then the cross-sectional area of the polygonal interior of the preceeding, up-stream scrubber section. The interior wear plates comprising the polygonal lining are removable and replaceable if they become worn or damaged.
U.S. Pat. No. 4,194,710 to Ebner relates to a tumbling mill with a generally polygonal, preferably square liner on the interior of the shell. At the corners, the liner plates are directly supported on the inside surface of the shell while elsewhere they are supported by spacers. The liner plates may have elevations, such as ribs or undulations, which cross the axis of rotation of the shell. The liner plates, which extend along elliptic arcs on the inside of the shell are amenable to individual replacement.
U.S. Pat. No. 4,211,369 to Eigner relates to a lining for tube or ball mills for wet or dry grinding systems. The lining is made up of a series of rings surrounded and distributed along the axis of the shell which are angularly offset, one with respect to the next, in a haphazard, nonuniform manner. Each of the rings defines an interior hollow space which has the configuration of a star having rounded points. Further, between the rounded star points, the hollow interior space of the mill has inwardly extending sharp corners to further reduce the amount of dead space in the interior of the mill and increase the number of impacts per revolution of the mill between the milling bodies and the material to be milled.
Finally, U.S. Pat. No. 4,485,975 to Eigner discloses an alternate apparatus for lining the interior surface of the shell of a tumbling mill. The lining includes a plurality of spaced liner rings which consist of interfitted liner plates and securing rings, each having a wedge-shaped cross-section and being situated between a pair of adjacent liner rings so that each liner ring is retained in position by a pair of securing rings. The securing rings themselves are fixed to the shell of the tumbling mill by bolts or the like.
The applicants have now discovered a novel and unobvious protective liner plate support for the shells of cylindrical grinding mills by developing an improved cylindrical segment, that may or may not be truncated, which is placed between the outer cylindrical grinding mill shell and the interior lining. The wear pieces of the cylindrical segment are easily replaced, which is a further advantage over the prior art.